title: Estimated albumin excretion rate versus urine albumin-creatinine ratio for the estimation of measured albumin excretion rate: derivation and validation of an estimated albumin excretion rate equation.
abstract: BACKGROUND
  Glomerular filtration rate estimation equations use demographic variables to account for predicted differences in creatinine generation rate. In contrast, assessment of albuminuria from urine albumin-creatinine ratio (ACR) does not account for these demographic variables, potentially distorting albuminuria prevalence estimates and clinical decision making.
  
  
  METHODS
  Polynomial regression was used to derive an age-, sex-, and race-based equation for estimation of urine creatinine excretion rate, suitable for use in automated estimated albumin excretion rate (eAER) reporting.
  
  
  METHODS
  The MDRD (Modification of Diet in Renal Disease) Study cohort (N=1,693) was used for equation derivation. Validation populations were the CRIC (Chronic Renal Insufficiency Cohort; N=3,645) and the DCCT (Diabetes Control and Complications Trial; N=1,179).
  
  
  METHODS
  eAER, calculated by multiplying ACR by estimated creatinine excretion rate, and ACR.
  
  
  METHODS
  Measured albumin excretion rate (mAER) from timed 24-hour urine collection.
  
  
  RESULTS
  eAER estimated mAER more accurately than ACR; the percentages of CRIC participants with eAER within 15% and 30% of mAER were 33% and 60%, respectively, versus 24% and 39% for ACR. Equivalent proportions in DCCT were 52% and 86% versus 15% and 38%. The median bias of ACR was -20.1% and -37.5% in CRIC and DCCT, respectively, whereas that of eAER was +3.8% and -9.7%. Performance of eAER also was more consistent across age and sex categories than ACR.
  
  
  CONCLUSIONS
  Single timed urine specimens used for mAER, ACR, and eAER.
  
  
  CONCLUSIONS
  Automated eAER reporting potentially is a useful approach to improve the accuracy and consistency of clinical albuminuria assessment.
authors.affiliation: Sheffield Kidney Institute, Sheffield, United Kingdom; School of Health and Related Research, University of Sheffield, Sheffield, United Kingdom.
authors.forename: James
authors.initials: J
authors.lastname: Fotheringham
authors.affiliation: School of Health and Related Research, University of Sheffield, Sheffield, United Kingdom.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Campbell
authors.affiliation: Queen's University Belfast, Belfast, United Kingdom.
authors.forename: Damian G
authors.initials: DG
authors.lastname: Fogarty
authors.affiliation: Sheffield Kidney Institute, Sheffield, United Kingdom; Global Kidney Academy, Sheffield, United Kingdom.
authors.forename: Meguid
authors.initials: M
authors.lastname: El Nahas
authors.affiliation: Sheffield Kidney Institute, Sheffield, United Kingdom; Department of Cardiovascular Science, University of Sheffield, Sheffield, United Kingdom. Electronic address: t.ellam@sheffield.ac.uk.
authors.forename: Timothy
authors.initials: T
authors.lastname: Ellam
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000419:Albuminuria / Q000652:urine*; D015415:Biomarkers / Q000652:urine; D003404:Creatinine / Q000652:urine*; D018753:Diet, Protein-Restricted; D018450:Disease Progression; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D051436:Renal Insufficiency, Chronic / Q000178:diet therapy / Q000652:urine*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D055815:Young Adult
chemical_list: D015415:Biomarkers; D003404:Creatinine
keywords: Albuminuria; albumin-creatinine ratio (ACR) correction; chronic kidney disease; creatinine; creatinine excretion rate (CER) prediction; proteinuria; urine albumin-creatinine ratio